Medical implants have wide-spread use in percutaneous vascular and cardiac surgery. These implants include, in particular, distal protection filter devices for the capture of thrombi in major veins such as the lower caval vein, occlusion devices for permanent or temporary obturation of a vessel lumen or permanent occlusion of defects in cardiac walls such as an atrial septal defect (ASD), a patent ductus arteriosus (PDA), or other cardiovascular defects such as, patent foramen ovale (PFO) and left atrial appendage (LAA).
Cardiac wall septal defects are usually congenital in nature leading to abnormal openings, holes or shunts between the chambers of the heart or the great blood vessels, causing abnormal shunting of blood through the opening. Such defects may result, for example, from the incomplete formation of the septum, or wall, between cardiac chambers during fetal life when the heart develops from a folded tube into a four chambered, two unit system. These deformities can result in significant health risks such as, high pulmonary arterial pressures and fatal heart failure, if not corrected.
Initially, atrial septal defects were corrected by open heart surgery. However, in order to avoid the morbidity and mortality associated with open heart surgery, a variety of transcatheter closure techniques have been attempted in patients. In such techniques, a medical implant such as an occluding device, is delivered percutaneously through an intravascular catheter into a patient. Once the occluding device is positioned adjacent the defect, it is attached to the wall adjacent the septum in a manner which permits it to effectively block the passage of blood through the defect. One such medical implant is a septal occluder which is inserted percutaneously via a catheter into a chamber of the heart to occlude a septal defect in a patient. A septal occluder is typically adapted very closely to the shape and size of the defect which is to be closed and is positioned very precisely upon implantation into the patient's heart. However, in the event that the septal occluder is dislodged from its intended location, or misaligned with the defect, it is often difficult to retrieve the septal occluder due to its shape or size. Furthermore, the process of retrieving the septal occluder often causes damage to the surrounding vasculature.
In addition to the use of medical implants for the treatment of septal defects, medical implants are also used to capture embolic debris caused by medical procedures that blood vessels stenosed or occluded in a patient caused by the deposit of plaque or other material on the walls of the blood vessels. Angioplasty, for example, is a widely known medical procedure wherein a dilating device, such as an inflatable balloon, is introduced into the occluded region of the vessel. The balloon is inflated, dilating the occlusion and thereby increasing intraluminal diameter. Plaque material may be inadvertently dislodged during angioplasty. This material is free to travel downstream, possibly lodging within another portion of the blood vessel that may supply a vital organ thereby causing damage to the organ by obstructing blood flow to the organ.
Medical implants such as distal protection filters are typically introduced into the desired blood vessel for capturing embolic debris dislodged during angioplasty. One of the problems associated with the removal of a medical implant such as a distal protection filter from a patient's body is that the retrieval process results in the collapse of the distal protection filter causing egress of particulate embolic matter back into the bloodstream. In the case of cerebral angioplasty, for example, emboli dislodged during the retrieval of a distal protection filter from a patient's body may travel to the brain, possibly causing a stroke, which can lead to permanent neurological injuries or even the death of the patient. Therefore, while distal protection filters are useful for trapping embolic debris that is dislodged or generated during a medical procedure, such as angioplasty, the egress of embolic debris trapped in a distal protection filter back into the bloodstream of a patient while the distal protection filter is being removed from the patient's body remains a problem.